Fix for eikek/docspell#2498. Added subPath to volume mount for postgres statefulset to make sure no conflicts happen on startup.

kubernetes/postgres.yaml

@@ -35,6 +35,7 @@ spec:
           volumeMounts:
             - name: postgres-data
               mountPath: /var/lib/postgresql/data
+              subPath: pgdata
   volumeClaimTemplates:
     - metadata:
         name: postgres-data
@@ -55,4 +56,4 @@ spec:
     - name: postgres
       port: 5432
       targetPort: postgres
-  clusterIP: None
+  clusterIP: None